1. Technical Field
The disclosure relates to light emitting devices and, more particularly, to a light emitting diode (LED) unit having a lens which can produce an effectively converged light beam.
2. Description of Related Art
LEDs, available since the early 1960's and because of their high light-emitting efficiency, have been increasingly used in a variety of occasions, such as residential, traffic, commercial, and industrial occasions. Conventionally, light directly output from the LED does not have a desirable pattern; therefore, a light-adjusting element, such as a lens, is used with the LED to adjust the light pattern thereof.
However, a typical lens generally has a limited light-converging capability; that is, the light passing through the lens cannot be effectively converged to have a small light-emission angle. Thus, the light pattern output from the lens may have a yellow annulus or shining annulus appearing at a periphery thereof, adversely affecting illumination effect of the LED.
What is needed, therefore, is an LED unit which can overcome the limitations described above.